Electrophysiology catheters are commonly used for mapping electrical activity in a heart. Electrophysiology is a specialty within the field of cardiology for diagnosis and treatment of electrical abnormalities of the heart. By mapping the electrical activity in the heart, ectopic sites of electrical activation or other electrical activation pathways that contribute to heart malfunctions may be detected. This type of information may then allow a cardiologist to intervene and destroy the malfunctioning heart tissues. Such destruction of heart tissue is referred to as ablation, which is a rapidly growing field within electrophysiology and obviates the need for maximally invasive open heart surgery.
Attached to the electrophysiology catheters are electrodes, which are used to map, or collect electrical information about, the electrical activity in the heart. It is also known to incorporate into certain electrophysiology catheters a location or position sensor for determining the location of the electrodes being used to map the electrical activity in the heart. Such catheters are generally inserted percutaneously and fed through one or more major blood vessels into a chamber of the heart. A location sensor in the catheter, typically near the catheter's distal end, produces signals that are used to determine the position of the device relative to a frame of reference, such as a position external to the body or within the heart itself. The location sensor may be active or passive and may operate by generating or receiving electrical, magnetic or ultrasonic energy fields or other suitable forms of energy known in the art.
U.S. Pat. No. 5,391,199, the disclosure of which is incorporated herein by reference, describes a position-responsive catheter comprising a miniature sensor coil contained in the catheter's distal end. The coil generates electrical signals in response to externally-applied magnetic fields, which are produced by field-generator coils placed outside the patient's body. The electrical signals are analyzed to determine the three-dimensional coordinates of the coil.
International Publication No. WO 96/05768, the disclosure of which is also incorporated herein by reference, describes a position-responsive catheter comprising a plurality of miniature, preferably non-concentric, sensor coils fixed in the catheter's distal end. As in U.S. Pat. No. 5,391,1999, electrical signals generated by these coils in response to an externally-applied magnetic field are analyzed so as to determine, for example, the six-dimensional coordinates of these coils, i.e. the positional coordinates and the orientational coordinates.
Multiple position-sensing devices may be placed in a known, mutually-fixed spatial relation at or adjacent to the distal end of a catheter, as described, for example, in International Publication No. WO 97/24983, the disclosure of which is incorporated herein by reference. This publication describes a catheter having a substantially rigid structure at its distal end, to which one or more position sensors are fixed. The sensors are used to determine the position and orientation of the rigid structure.